The grinding of a variety of materials can have a desirable effect. For instance, grinding of some types of waste results in increased rate of decomposition, which is useful in landfill operations; grinding wood waste produces mulch that is useful in landscaping applications; and grinding asphalt is useful in recycling efforts. Some types of shingles can also be ground for use in asphalt production. The benefits of and need for such recycling processes continue to grow.
Several types of machines are used in grinding applications. One type is known as a horizontal grinder. An example of a horizontal grinder is disclosed in U.S. Pat. No. 5,881,959. Horizontal grinders typically include a horizontal feed table onto which material to be ground is placed. The feed table is capable of moving the material to a point where a feed roller begins to cooperate with the feed table. The feed roller generally presses down on top of the material, while being rotationally powered, to assist in forcing the material into contact with the side of a grinding drum.
The grinding drum is as wide as the feed table and rotationally powered on a generally horizontal axis perpendicular to the direction of travel of the feed table. The grinding drum typically includes hammers or cutters mounted to the outer perimeter of the drum to impact the material as it is fed from the feed roller/feed table. These hammers or cutters tend to propel the material either up, for grinders known as up-cut grinders, or down, for grinders known as down-cut grinders. Down-cut grinders force the material past a stationary bar, typically known as an anvil, which is in relatively close proximity to the outer swing diameter of the hammers or cutters. Because of the anvil's relative close proximity, the size of the outer swing diameter is reduced, as necessary, to travel past the anvil. Once the material passes the anvil, the material is further reduced, as necessary, to pass through a screen.
In the '959 patent, a primary anvil is positioned a slight distance from the grinding drum such that a primary grind will occur as the material is forced past the primary anvil. The material is further reduced at a secondary anvil. If the material is ungrindable, the material passes through a trap door positioned between the primary and secondary anvils. This arrangement involves several components and moving parts that add complexity to the overall design of the grinder.
An alternative design, marketed by Vermeer Mfg (Model HG525) includes a single anvil that is located in close proximity to the grinding drum such that any material that passes by this single anvil, is capable of passing through the screens. Ungrindable material is typically retained in the feed conveyor where it can more easily be removed manually. Since the grinding drum is typically rotating such that cutters mounted to the outer perimeter of the drum are traveling at a high rate of speed, any ungrindable material is subjected to highly dynamic impact loading. The dynamic impact loading is then transferred to this single anvil, or the feed table adjacent the anvil. In certain instances, the loading can be sufficient enough to damage the anvil and supporting structure. A robust, replaceable anvil and supporting structure is thus advantageous. In other cases, highly abrasive material is processed, which wears away the anvil. It is desirable to easily maintain the anvil if wear is excessive; a removable anvil facilitates such maintenance.
In general, improvement has been sought with respect to such arrangements, generally to better accommodate: ease of use, assembly, and maintenance; and improved component and equipment life.